It is known that electrostatic discharge (ESD) can cause catastrophic failure in integrated circuit components. A number of proposals have been advanced to protect against such ESD damage which can occur during handling of circuits prior to installation as well as contact after installation. In automotive instrument clusters containing printed circuit boards it is known to cover the back of the board which would otherwise be exposed during assembly of the vehicle and during operation thereafter to isolate the circuits from the ESD sources.
In most ESD protective devices for instrument clusters, a protective panel is secured to the rear of the cluster, spaced from the circuit board. The panel may be sheet metal, for example, wherein the metal dissipates any build-up of charge and also prevents the intimate approach to the circuit board of any object bearing such a charge. Insulating panels have been used in the same manner, acting as a guard against approach, the insulating material itself and the air space between the panel and the circuit board resisting dielectric breakdown due to a high voltage. In some cases a composite or laminate material having both conductive and insulating components are used. It is also known to apply a laminate material directly to the back of the circuit board; such material comprises an insulating inner layer against the circuit board and a conductive foil as an outer layer.
All the panels previously used for instrument cluster ESD protection are expensive, using an expensive material and/or expensive tooling for forming the panels. In the case of sheet metal, the metal is expensive as well as the stamping dies. Insulating covers are often made by injection molding or vacuum forming plastic; in those cases the forming equipment is expensive.